Comprehensive analysis of electrolyte solutions for lithium- ion batteries using gas chromatography-mass spectrometry

Importance of the Topic

Advances in lithium‐ion battery (LIB) performance, safety, and lifetime depend heavily on detailed knowledge of electrolyte composition and its transformation under cycling. Electrolytes define ion transport, interphase formation, and stability at elevated temperatures. As the world transitions to electric vehicles and renewable energy storage, analytical methods that deliver rapid, sensitive, and comprehensive profiling of electrolyte solvents, additives, and degradation products are critical for guiding formulation improvements and quality control.

Aims and Study Overview

This application note presents a robust gas chromatography–mass spectrometry (GC-MS) workflow for quantitation and characterization of 16 key electrolyte components. The study demonstrates the capabilities of a single‐quadrupole GC-MS equipped with a high‐dynamic‐range XLXR detector to achieve accurate analysis across concentration ranges spanning several orders of magnitude. Both fresh and cycled electrolytes are compared to identify compositional changes and trace degradation products.

Methodology and Instrumentation

An external calibration series covering 0.1 to 200 mg·L⁻¹ (full scan) and 0.1 to 100 mg·L⁻¹ (SIM) was prepared in dichloromethane. Sample extraction involved dilution of 20 µL electrolyte in 1 mL solvent, centrifugation to remove LiPF₆, and serial dilutions up to 1:50 000. Chromatographic separation utilized a TRACE 1610 GC with TraceGOLD TG-35 MS column (30 m × 0.25 mm × 0.25 µm), split injection (1 µL, split ratio 1:20), and a temperature program from 35 °C to 200 °C in 23 min total run time. MS detection combined full scan (m/z 35–500) with timed‐SIM acquisition for low‐level components.

Instrumentation

• Thermo Scientific ISQ 7610 single quadrupole GC-MS with XLXR electron multiplier detector
• Thermo Scientific TRACE 1610 gas chromatograph
• Thermo Scientific TriPlus RSH autosampler
• TraceGOLD TG-35 MS capillary column

Main Results and Discussion

Full scan analysis achieved baseline separation of 16 analytes within 16 min. Calibration curves exhibited linearity over four orders of magnitude (r² > 0.99 for most compounds), with instrument detection limits between 0.003 and 0.021 µg·L⁻¹ and quantification limits below 0.07 µg·L⁻¹. SIM acquisition improved sensitivity for low‐abundance additives such as vinylene carbonate and ethyl propionate, confirming their presence in cycled samples where full scan alone failed.

Comparison of new electrolyte batches revealed variation in solvent ratios (e.g., diethyl carbonate vs ethyl methyl carbonate dominance), while cycled electrolytes showed accumulation of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and phenylcyclohexane. NIST library searches on full scan data identified biphenyl as a flame‐retardant additive and dioxahexane acid dimethyl ester as a known degradation product. A minor peak putatively assigned to 1,4‐mercapto‐2,3‐butanediol requires further standard‐based confirmation.

Benefits and Practical Applications

• Rapid, high‐throughput screening of fresh and aged electrolytes with run times under 25 min
• Wide dynamic range enabling simultaneous analysis of high‐volatility solvents and trace additives
• Low detection limits supporting early identification of degradation pathways
• Combination of full scan for unknown discovery and SIM for targeted confirmation

Future Trends and Applications

Ongoing developments include integration with automated sample handling for in‐line battery testing, expansion of analyte libraries to cover next‐generation salts and solvent blends, and coupling with high‐resolution MS for untargeted profiling of emerging degradation species. Advances in software‐driven deconvolution will further streamline identification of trace components in complex matrices.

Conclusion

The Thermo Scientific ISQ 7610 GC-MS with XLXR detector offers a powerful solution for comprehensive electrolyte analysis, delivering rapid separation, broad dynamic range, and sensitive detection of solvents, additives, and byproducts. This approach supports formulation optimization, quality control, and failure analysis in lithium‐ion battery research and manufacturing.

Reference

• Campion CL, et al. Thermal Decomposition of LiPF₆-Based Electrolytes for Lithium-Ion Batteries. J Electrochem Soc. 2005;152:A2327–A2334.
• Zhang SS. A review on electrolyte additives for lithium-ion batteries. J Power Sources. 2006;162:1379–1394.
• Horsthemke F, Friesen A, Mönnighoff X, et al. Fast screening method to characterize lithium-ion battery electrolytes by solid‐phase microextraction–GC–MS. RSC Adv. 2017;7:46989–46998.